It may very well be the second most famous equation of all time, outshone only by that braggart Einstein’s mass–energy equivalence equation. But for those of us that aren’t theoretical physicists, the Pythagorean Theorem is likely to play a fundamental role in many of the calculations we do whether we realize it or not.

Everyone knows the equation, but before we get into it’s proof, let’s re-cap what it means. Consider the following right triangle:

This triangle has sides and hypotenuse . The Pythagorean Theorem simply tells us then that the square of the length of the hypotenuse () is equal to the square of the length of side plus the square of the length of side (). Well, duh. And after we learn it in middle school many of us take it as axiomatic, but it does have “theorem” in it’s name so I feel its worth revisiting it’s proof every once in a while to keep me on my toes.